Commercial products need product label to provide product information for customers' purchase decision and to meet regulatory requirements. Product information consists of static information, such as ingredients, and dynamic information, such as the production date, times, expiration date, control number, and lot number. The static information can be preprinted on product label in print shop, but dynamic information will need to be printed in a real-time basis according with the time of production and the sequence of the production. This real-time printing is an information coding printing system. Most of the product label coding systems are installed in the production line to work with product packing system. The printed codes on the label must have high clarity for legibility under a high speed printing process.
In the current market, there are two major types of label coding printing systems: contact type or noncontact type. Thermal transfer ribbon printing represents one kind of contact type printing system. A thermal transfer ribbon printing system utilizes a ribbon coated with adhesive printing substrate. The printer head with printing pints presses the ribbon to contact with label or printing object, heats the printing pints to melt adhesive printing substrate onto the label or the surface of the printing object, and allows the coding information to be adhered on the label or the surface of a printing object. The disadvantages of the thermal transfer ribbon systems include the slow speed of the printing process, the waste of unused portion of the thermal ribbon, the size of thermal printer head to cover printing area, and the complex mechanical structures causing the downgrade of the thermal printer head.
Noncontact type printing system includes laser printer and inkjet printer. Laser printing system utilizes a label containing a top coating and a colorant base coat. The laser burns out the top coat and reveal the colorant to present the coding information. The disadvantage of the laser printing system is the high cost of the system, the complexity to reconfigure the production line to fit the laser printing system, and the hazardous gas causing environmental concerns. The other noncontact type printing system is inkjet printing system. The inkjet printing system is smaller and simpler than thermal transfer ribbon system or laser printing system. It utilizes a replaceable printing cartridge that have rows of ink nozzles to inject printing substrate onto a label or the surface of a print object. Inkjet printing system has shorter printing time than thermal transfer ribbon, no wear of inkjet printer head as thermal transfer ribbon, and no waste of unused material like thermal ribbon. It is also a better system than the laser printing system for its simplicity, lower cost, and no hazardous gas.
However, the inkjet printing systems available in the current market and industry have several issues. Due to the technical obstacle, the current printer head and the printing objects are arranged to move horizontally. The printer head or the material/label moves horizontally. The direction of the rows of the ink nozzles of the inkjet printing cartridge is perpendicular to the travel direction of the label or the printing object, and the ink nozzles inject ink onto the label or the printing object while the label or the printing object is moving. The ink nozzles of the inkjet printer inject ink in accordance with a constant traveling speed of the label or the printing object passing under the ink nozzles. However, it is hard to control the traveling speed of the label or printing object on a production line. The factors affecting the control of traveling speed may include but not limited to the material of label, the thickness of label, the temperature, the humidity, and size of the label or printing material.
Also, the stationary location of the inkjet printer is hard to adjust in accordance with different size and location of the printing object, such a small can or a large bottle. Currently, it needs to dismount the inkjet printer, adjust its location, mount the inkjet printer, and adjust the printer again. If the location is not right, the adjustment process will need to be repeated.
Another common issue to inkjet printer is that the ink nozzles will have some printing ink buildup around the ink nozzles. When inkjet printer is not working, the buildup of the ink will be dried out and clog the ink nozzles. It needs an ink cleaning or ink purge system to clean the ink nozzle regularly. Current industrial application of the cleaning method is by manual clean, which increases the system downtime and does not a consistent clean result.